This invention relates to a charge air cooler for use in a turbocharging loop of an engine.
Turbochargers are frequently used in order to compress more air within engine cylinders to allow more efficient combustion with fuel, reducing wasteful emissions and increasing the power gained from each piston stroke. A consequence of compressing air is that its temperature increases which reduces the density of the charge air, increases nitrous oxide emissions and can lead to premature aging of the engine.
It is known to provide a charge air/air cooler between the turbocharger and engine cylinders in order to cool the compressed air and mitigate these problems. However, in order to meet increasingly strict emission regulations, charge air pressure must be significantly boosted (up to 4to 1) which results in a temperature increase to over 500 F (260° C.). This temperature increase results in the temperature of known charge-air coolers to increase beyond their operational design limit.
High thermal stresses are also created by the temperature difference between the cooling air and charge air. As a result, charge air cooler life is significantly reduced.
US Patent Application US20030037917A1 describes the use of a cooler utilizing liquid coolant which can be provided upstream of a conventional charge air/air cooler. However the radial dispersion of the charge air reduces the charge air pressure due to the change in direction of the charge air, resulting in a pressure loss and lower pressure boost. Moreover, the use of a separate cooler reduces the pressure of the charge air since the air must enter and exit two coolers, suffering pressure losses each time.
U.S. Pat. No. 6,755,158 also discloses a cooler which utilizes liquid coolant but suffers from the same disadvantage of pressure loss due to the provision of a separate cooler.